T-square.



PATENTED AUG. l5, 1905.

J. A. ROBINSUN, T-SQUARE. APPLICATION FILED AUG. 27, l90 4.

NTTED STATES PATENT- GFFICE.

'lV-SQUARE..

no. ramas.

Specification of Letters Patent.

:Patented` Aug. 15, 1905.

Application filed August 27, 1904. Serial No 222,673.

To all whom t may concern:

Be it known that l, JAMES ARTHUR ROBIN* SON, a citizen of the UnitedStates, residing' at Bellville, in the county of Richland, State ofUhio,have invented certain new and useful Improvements in 'IF-Squares;andl doherebydeclare thefollowing to be a full, clear, and exactdescription of the invention,such as will enable others skilled in theart to which it appertains to make and use the same.

This invention relates to T- squares, and more particularly toadjustable lf-squares, and has for its object to provide a device ofthis nature which will be so arranged that it may be set to any angleand which will be pro vided with a scale in order that the deg'ree ofthe angle may be exactly determined.

A further object is to provide a 'IV-square embodying' these featureswhich will be strong and durable and which may be manufactured at a lowcost.

@ther objects and advantages will be apparent from the followingdescription, and it will be understood that modilications of thespecilic construction shown may be made and any suitable materials maybe used without departing from the spirit ef the invention.

ln the drawings forming a portion of this specification, and in whichlike numerals of reference indicate similar parts in the several views,Figure l is a plan view of the present invention. Fig. 2 is a section online 2 2 of Fig. 1. Fig. Sis a section en line 3 3 of Fig. 1.

Referring new to the drawings, the present invention comprises a headhaving' a plate 6 secured to its upper face and formed integ'ral withthe plate and extending outwardly therefrom at opposite points, andextending longitudinally of the head 5 are arms 7, and formed integrallywith these arms is a seg'- ment 8, which joins the arms 7 at its ends,and this segment 'is marked ofi' in a scale, as illustrated, theseg'ment projecting beyond the rearward edg'e of the head and being' inreality a semicircle.

liormed centrally through the head 5 is an opening 9, and securedagainst the under face of the head is a plate 110, having an opening' 10therein, and formed through the plate (S is an opening` 6', which alsoalines with the opening' 9 for the reception of a bolt 1l, whichvextends above the head. Formed upon the plate 6 and concentric with theopening 6 is an angular rib l2 for a purpose to be presentl y described.

The blade 13 of the T-square has one of its ends disposed in recess 14in a plate 15, the upper face of the blade lying' flush with the face ofthe plate, and secured against the blade and the plate is another plate16, the plates 15 and 16 and the blade having alining perforations 17therethrough, in which is revolnbly engaged the bolt 11. The plate 15 isprovided with an angular groove 18 for the reception of the rib l2, andengaged with the end ofthe bolt11,which projects beyond the plate 16,isa wing-nut 19, by means of which the bladeI may be clamped against thehead to prevent movement ol the two portions with respect to each other.Projecting outwardly from the plate 15 beyond the rearward edge of thehead 5 is a lug 20, having' a threaded perforation 21 therein, and theouter end of this lug :is received in a recess 9.2 in the under face andat the end of a 'linger 23, having a passage 2a alining with theperforation 2l for the reception of a screw 25 to hold the finger to thelug. The outer end of the lug is beveled, and the recess 22 is similarlybeveled. The iinger 23 projects over the segment 8 to indicate the scalethereon, which, as illustrated, eX' tends through ninety degrees of acircle, and when in use when it is desired to draw a line ata certainangle the wing-nut 19 is loosened and the blade is moved with respect tothe head until the finger indicates the desired anglc, after which thewing-nut is tightened, and the line may be drawn in the usual manner.

What is claimed is---- In a 'lV-square the combination with a headhaving an opening formed therethrough, of plates secured to the upperand lower faces of the head respectively, said plates having openingstherethrough alining with the opening of the head, oppositely-extendingarms formed integral with the upper plate and extending longitudinallyof the head, a segment connected at its ends with the ends of the armsand formed integral therewith, said segment having' a scale markedthereon, a bolt engaged in the alining openings of the head and platesand extending above the upper plate, a plate having an opening' in whichthe bolt is engaged above the upper plate of the head, said third-namedplate having a recess in its upper face, a blade disposed at one end inthe recess and having an opening' alining with the opening of thethird-named plate, and in which the bolt is engaged, the upper face ofthe blade lying flush with the upper face of the third plate, a fourthplate disposed upon the flush faces of the blade and the third plate,fastening devices engaged in the fourth plate and in the blade,fastening devices enf gaged in the fourth plate and Ain the third plate,said segment extending rearwardly of the head, an outwardly-projectinglng earried by the third plate at its rearward edge,

said lug having a beveled rearward end, a l

linger having a beveled recess in which the lug is engaged, a fastening'device removably engaged in the lug and in the finger, said tingerprojecting over the segment and being '3 arranged for movementthereov'er when the l third plate is moved, and a clamping-nut engagedWith the bolt above the fourth plate g foroperation topreventmovementofthe blade npon thebolt.

